WASHINGTON —Reaction at the White House and on Capitol Hill to the slayings at Fort Hood was one of shock and horror, with officials promising a full investigation and offering their prayers for the dead and injured.

“These are men and women who have made the selfless and courageous decision to risk, and at times give, their lives to protect the rest of us on a daily basis,” a somber President Barack Obama said in brief remarks.

Hutchison, speaking without notes, asked her colleagues to observe the moment of silence “in memory of 11 great soldiers at Fort Hood, Texas, who have been shot down this afternoon at the base” at a processing center where they were being prepared to be deployed to Iraq and some to Afghanistan.

A Texas aide to U.S. Rep. John Carter was at the Army post for a ceremony when the shooting occurred. The aide witnessed men running, some bleeding.

“Our office offers up our greatest condolences to the soldiers and their families. We're praying for all those involved,” said Carter, R-Round Rock, whose district includes the post.

Obama promised to put the resources of the federal government behind the investigation and to support the Fort Hood and Killeen communities.

“We will make sure we get answers to every single question about this horrible incident,” he said.

In Texas, Gov. Rick Perry canceled a fundraiser in Waxahachie and a grassroots event in Waco, said spokesman Mark Miner.

“We have the right people on the scene,” Perry said, speaking in Denton. “Certainly at some point in time, I may be on site, but not until I am not a distraction to any of the events that are going on there.

“God bless you, and keep these people in your prayers today,” Perry said.

The governor also issued a statement that said he had ordered all Texas flags lowered to half-staff until Sunday.

Sen. John Cornyn, R-Texas, called Fort Hood “one of our nation's finest and largest military installations, and a place that has long been a source of pride for Texans, and for all Americans who value the selfless service and sacrifice of our men and women in uniform.

“It is imperative that we take the time to gather all the facts, as it would be irresponsible to be the source of rumors or inaccurate information regarding such a horrific event. ... My prayers are with the individuals who were killed today, the wounded and their loved ones.”

U.S. Rep Al Green, D-Houston, said he hoped a thorough investigation “will clarify what has happened and will bring justice.“

And Defense Secretary Robert Gates, whose close ties to Texas include a stint as president of Texas A&M University, expressed his sadness.

“There is little we can say at this point to alleviate the pain or answer the many questions this event raises, but I can pledge that the Department of Defense will do everything in its power to help the Fort Hood community get through these difficult times.”